WASHINGTON — Several US lawmakers received threatening letters containing a harmless white powder, but the sender warned more missives including a “harmful material” could follow, a Senate official said.

The news sparked alarm and served as a grim reminder of the 2001 anthrax attacks in which letters containing the deadly pathogen were sent to offices of two Democratic senators and several media offices. Five people were killed.

The anonymous sender “has indicated that additional letters containing a powdery substance will be arriving at more Senate offices,” Senate sergeant-at-arms Terrance Gainer said in a email to staff.

“Some of these letters may contain an actual harmful material,” he added, noting the missives were postmarked from Portland, Oregon.

Similar letters, which included complaints about corporate influence over US politics, also were received by several US media outlets, but they did not contain any white powder, said law enforcement officials quoted by US media.

The letters were received by organizations such as The Washington Post, The Los Angeles Times, USA Today, Fox News and National Public Radio, reports said.

CBS News quoted a law enforcement official as saying that in missives to comedians Jon Stewart and Stephen Colbert, the sender warned that 100 letters were sent to the Washington or home-state offices of US senators.

A Time Magazine 'Person of the Year' argues WikiLeaks serves the public good

A member of a group of former intelligence professionals that has rallied behind WikiLeaks suggested in a recent interview with Raw Story that the world would be a different and better place had the online secrets outlet come into existence years sooner.

“If there had been a mechanism like Wikileaks, 9/11 could have been prevented,” Coleen Rowley, a former special agent/legal counsel at the FBI's Minneapolis division, told Raw Story in an exclusive interview.

If WikiLeaks had been around in 2001, could the events of 9/11 have been prevented? The idea is worth considering.

The organization has drawn both high praise and searing criticism for its mission of publishing leaked documents without revealing their source, but we suspect the world hasn't yet fully seen its potential. Let us explain.

There were a lot of us in the run-up to Sept. 11 who had seen warning signs that something devastating might be in the planning stages. But we worked for ossified bureaucracies incapable of acting quickly and decisively. Lately, the two of us have been wondering how things might have been different if there had been a quick, confidential way to get information out.

Two years before the 9/11 attacks on America, George W. Bush told a Houston journalist if elected president, “I’m going to invade Iraq.”

Bush made the comments about starting an aggressive war to veteran Houston Chronicle reporter Mickey Herskowitz, then working with Bush on his book “A Charge To Keep,” later brought out by publisher William Morrow.

This disclosure was uncovered by Russ Baker, an award-winning investigative reporter when he interviewed Herskowitz for his own book, “Family of Secrets” (Bloomsbury Press) about the Bush dynasty. However, Baker says, when he approached The Washington Post and The Los Angeles Times with the potentially devastating story to President Bush prior to the 2004 presidential election, they declined to publish it.